See this on a psychrometric chart
Want to plot two state points and visualize the process line — sensible cooling, mixing, dehumidification? AIM Works draws the full chart — saturation curve, RH grid, and process line — from the same psychrometric math. It launches October 15, 2026.
Doing this for a whole building? See this step inside a connected AIM Works project — loads, ventilation, equipment, and Design Review in one place.
Book a Demo →This psychrometric calculator returns the full moist-air state from just two known conditions: dry-bulb temperature plus relative humidity, wet bulb, or dew point. It reports humidity ratio (in lb/lb and grains per pound), enthalpy, specific volume, relative humidity, wet bulb, dew point, water-vapor pressure, and the barometric pressure used — everything you would otherwise read off a psychrometric chart.
Engineers use these properties to size cooling and heating coils, estimate latent versus sensible loads, check condensation risk, and design dehumidification and economizer sequences. Because the tool derives barometric pressure from your elevation, the results stay accurate at altitude where sea-level psychrometrics would over-predict density.
| Saturation pressure | Pws: Hyland–Wexler equations (over ice below 32 °F, over liquid water above) |
| Barometric pressure | P = 14.696 · (1 − 6.8754×10−6 · Z)5.2559 psia, Z = elevation (ft) |
| Humidity ratio | W = 0.621945 · Pw ÷ (P − Pw) |
| Enthalpy | h = 0.240 · T + W · (1061 + 0.444 · T) |
| Specific volume | v = 0.370486 · (T + 459.67) · (1 + 1.607858 · W) ÷ P |
| Wet bulb | W = [(1093 − 0.556·Twb)·Ws,wb − 0.240·(T − Twb)] ÷ (1093 + 0.444·T − Twb), solved for Twb (ice form below 32 °F) |
| Dew point | Pws(Tdp) = Pw, solved numerically |
Every relation is the ASHRAE Handbook—Fundamentals (2021) Chapter 1 moist-air equation set in IP units (T in °F, P in psia), in their ideal-gas form; rigorous real-gas formulations differ by well under 1 % in W at HVAC conditions. Vapor pressure is Pw = RH · Pws. Barometric pressure comes from your elevation through the standard atmosphere (14.696 psia at sea level), so every output is altitude-corrected. Wet bulb is the thermodynamic (adiabatic-saturation) wet bulb, which a well-ventilated sling psychrometer reads closely. Below 32 °F the dew point is taken over ice (the frost point). Valid for dry bulb from −60 to 200 °F.